As development of Short Messaging Service (SMS) and Enhanced Messaging Service (EMS), MMS provides a complete end-to-end solution for personal multimedia mobile communication services. In terms of communication content, multimedia messages include images, audios, videos and data, etc.; and in terms of function, MMS covers multimedia message communications from terminal to terminal, from terminal to application and from application to terminal. With MMS, not only communications between terminals and between terminal and application can be realized, but also the diversity of contents, including different combinations of pictures, voices, images, data and texts, can be realized. As an open media service access platform, MMS can be used to derive rich and colorful content service applications through interactions between mobile users and Internet content providers. During this process, the users act not only consumers of MMS, but also content developers, so the interests of terminal users for employment of the service will be undoubtedly raised.
The prepaid MMS has been treated as one of important services to start and develop 2.5G and 3G data service. The prior prepaid MMS adopts Wireless Application Protocol (WAP) events to deal with the procedures. In prior prepaid MMS, information is actively obtained from multimedia message centers by recipients, which is the same as the browsing or downloading method in WAP and different from SMS in network architecture and charge mode.
The subscribers of prepaid MMS form an important part of mobile users. The prepaid MMS aims to provide complete MMS for prepaid users, making mobile users of prepaid MMS be able to enjoy various MMSs at anytime and anywhere as postpaid subscribers do.
About prepaid MMS, the specification of the Third Generation Partnership Project (3GPP) describes as follows.
The Multimedia Messaging Service Center (MMSC) can support prepaid MMS. When a calling subscriber submits a multimedia message, if the originator MMSC confirms that the originator of the multimedia message is a prepaid MMS subscriber, the originator MMSC will transmit a charge request to a Service Control Point (SCP) and carry out authentication and charge verification. If there is no enough account balance for the subscriber to pay for the multimedia message, the originator MMSC can deny the message. The specific standards to determine whether the account balance is enough to pay for the multimedia message are based on following terms: total size of the multimedia message, type of content, configuration of message elements and type of abstract message.
Procedure of authentication and charge verification made in originator MMSC is as follows. At first, SCP makes authentication on MMSC. If the calling subscriber is a terminal user or an E-mail address user, then the charge rate will be designated by MMSC, and SCP will make verification and deduction according to the charge rate and payable balance of the calling subscriber. If the calling subscriber is a user of Value Added Service Provider (VASP), then the charge rate and charge mode will be determined by VASP, and SCP will make verification and deduction according to the charge rate, the charge mode and payable balance of the calling subscriber.
Once the multimedia message is refused, the originator MMSC should prompt originator MMS terminal with response of suitable status value, and the MMS terminal should prompt the subscriber to pay attention to the message. If authentication for the multimedia message from originator made by SCP is successful, then SCP will ask the MMSC to distribute the message.
When extracting the multimedia message, the recipient MMSC will confirm whether the recipient of the multimedia message is a prepaid MMS user firstly, and check account balance for the confirmed subscriber. The checking operation can be implemented at the time when the multimedia message arrives the recipient MMSC, at this time, the MMSC can deny or accept the multimedia message according to the checking result. Even the multimedia message is accepted, it is not certain whether the multimedia message has been checked in advance, so the MMSC can also check the account balance when the recipient MMS terminal sends an extracting request, wherein the checking is based on the same standard as that while sending messages. If the multimedia message cannot be extracted because of no enough account balance, the recipient MMSC should prompt the recipient MMS terminal with response of suitable status value, and the recipient MMS terminal will remind the subscriber to pay attention to the message. Otherwise, the multimedia message will be sent to the recipient MMS terminal.
After sending the message to the recipient MMS terminal, the MMSC will send a charge confirmation request to SCP, in order to enable SCP to implement the accurate charge operation.
The specifications on prepaid MMS in 3GPP are relatively simple, only some fundamental principles about prepaid MMS are described on the whole, but no further solution on methods for prepaid MMS is provided. Some of its defects are listed as follows.
(1) There is no corresponding specification on prepayment interface for prepaid MMS, that is, there is no interface protocol and definition of message architecture about the interface between MMSC and SCP.
(2) The problems of message interacting procedure keep unsolved between terminal and terminal, or terminal and VASP application in prepaid MMS.
(3) The charge problems on the prepaid MMS are only skimmed over in 3GPP, without any perfect solution on charge mechanism for prepayment being provided.